Bone pads

ABSTRACT

Disclosed herein are systems and methods for bone preparation with designed areas having accurate tolerance profiles to enable improved initial fixation and stability for cementless implants and to improve long-term bone ingrowth/ongrowth to an implant. A method of preparing a bone surface to receive a prosthetic implant thereon having an articular surface and a bone contacting surface includes resecting the bone surface at a first location to create a first resected region having a first tolerance profile with a first cross-section, resecting the bone surface at a second location to create a second resected region having a second tolerance profile with a second cross-section less dense than the first cross-section, and contacting the bone contacting surface of the prosthetic implant with the first resected region.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/195,113, filed on Mar. 3, 2014, which claims the benefit of thefiling date of U.S. Provisional Patent Application No. 61/775,045, filedMar. 8, 2013, the disclosures of which is hereby incorporated herein byreference.

BACKGROUND OF THE INVENTION

In a traditional knee arthroplasty surgery, the diseased bone and/orcartilage of a patient is generally removed and replaced with aprosthetic implant. A surgeon may prepare the bone using a hand-heldoscillating saw blade, for instance, which generally results in a seriesof planar bone surface resections. Additionally, the surgeon may use adrill, broach or tamp instrument to make cylindrical holes into the boneto accommodate peg fixation features on the implant. The planar boneresections and cylindrical bone holes are generally oriented tointerface with generally flat bone contacting surfaces and pegs of aprosthetic implant.

In such arthroplasty surgeries, the cartilage and/or bone of a patientmay be prepared by a surgeon using conventional manual instrumentation.The instrumentation used may include, for example, planar resectionguides, oscillating saws, drills, chisels, punches and reamers.

Robotic surgery may also be used in arthroplasty procedures, as well asin many different medical applications. The use of a roboticallycontrolled bone preparation system allow for increased accuracy andrepeatability of bone preparation. Rotational preparation instrumentsmay be used during robotic surgery to prepare the bone and/or cartilagesurfaces.

Bone preparation using these known methods generally provides surfacesof variable accuracy. Further, implant surfaces are generally preparedwith the same level of consistency across the entire prepared bonesurface. These methods of bone preparation may have a negative effect onthe initial fixation of a cementless implant. If the surface does notprovide a stable base for a cementless implant when initially fixed tothe bone, the long term success of bone ingrowth/ongrowth onto theimplant may be compromised due to micromotion, which may lead to fibrousingrowth and subsequent bone resorption.

With advancements in robotically controlled bone preparation systems,bone preparation with specifically designed regions having increasedlevels of accuracy are now considered. Therefore, robotic bonepreparation enables select aspects of the bone to be prepared at agenerally more accurate and “tighter” tolerance compared with alternatemethods of bone preparation. The degree of accuracy to which aprosthetic implant is implanted on a prepared or resected bone throughrobotic control depends on several factors. Among those factors includethe tolerance to which the prosthetic implant is manufactured or know,the tolerance of any required tracking equipment used to position therobotic arm, and the tolerances of the robotic arm itself.

BRIEF SUMMARY OF THE INVENTION

The present invention includes bone preparation with designed areashaving accurate tolerance profiles to enable improved initial fixationand stability for cementless implants and to improve long-term boneingrowth/ongrowth to an implant. Further, the present invention includesnew methods of implanting an implant onto these accurate toleranceprofiles.

A first aspect of the present invention is a method of preparing a bonesurface to receive a prosthetic implant thereon, the prosthetic implanthaving an articular surface and a bone contacting surface. The methodincludes resecting the bone surface at a first location to create afirst resected region having a first tolerance profile with a firstcross-section. The method further includes resecting the bone surface ata second location to create a second resected region having a secondtolerance profile with a second cross-section, the cross-section of thefirst tolerance profile being denser that the cross-section of thesecond tolerance profile. The method further includes contacting thebone contacting surface of the prosthetic implant with the firstresected region.

In one embodiment of this first aspect the method further includesforming at least one recess in the bone surface prior to implanting theprosthetic implant on the bone surface, and inserting a retentionelement extending from the bone contacting surface in the at least onerecess in the bone surface.

In another embodiment of this first aspect the method includes applyingdownward force to the articular surface of the prosthetic implant tocompact bone in the first resected region.

In yet another embodiment of this first aspect the method includesresecting the bone surface at a plurality of locations to create aplurality of resected regions each having a tolerance profile with across-section, wherein the tolerance profile of each of the plurality ofresected regions is denser that the cross-section of the secondtolerance profile.

In still yet another embodiment of this first aspect the first of theplurality of resected regions is preferably located at an anterioraspect of the bone. The second of the plurality of resected regions ispreferably located at an outer aspect of the bone. The third of theplurality of resected regions is preferably located at a posterioraspect of the bone.

In still yet another embodiment of this first aspect the cross-sectionof the tolerance profile of a first of the plurality of resected regionsis less dense than the cross-section of the tolerance profile of asecond of the plurality of resected regions and is more dense that thecross-section of the tolerance profile of a third of the plurality ofresected regions.

In still yet another embodiment of this first aspect the toleranceprofile of the second resected region is preferably ±0.010 inches andthe tolerance profile of the plurality of resected regions is preferably±0.025 inches. In other embodiments, the tolerance profile of the secondresected region and plurality of resected regions may be more or lessthan ±0.010 inches and ±0.025 inches, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood on reading the followingdetailed description of non-limiting embodiments thereof, and onexamining the accompanying drawings, in which:

FIG. 1 is a perspective view of an embodiment of the present inventionof a prepared tibial bone surface with tolerance profiles.

FIG. 2 is a top view of the tibial bone surface with tolerance profilesfrom FIG. 1.

FIG. 3 is a cross-sectional perspective view of another embodiment ofthe present invention of a prepared bone surface with toleranceprofiles.

FIG. 4 is a front view of the perspective view shown in FIG. 3.

FIG. 5 is a perspective view of an embodiment of a unicondylar tibialimplant.

FIG. 6 is a top view of another embodiment of the present invention of aprepared tibial bone surface with tolerance profiles.

FIG. 7 is a perspective view of another embodiment of the presentinvention of a tolerance profile.

FIG. 8 is a cross-sectional view taken along line B-B of the toleranceprofiles shown in FIG. 7.

FIG. 9 is a cross-sectional view of another embodiment of the presentinvention of a tolerance profile.

FIG. 10 is a perspective view of one embodiment of the present inventionof a prepared femoral bone with tolerance profiles.

FIG. 11 is a view from a posterior aspect of the prepared femoral bonewith tolerance profiles shown in FIG. 10.

FIG. 12 is a view of a distal bone contacting surface of a unicondylarfemoral implant.

FIG. 13 is a view of a posterior bone contacting surface of theunicondylar femoral implant from FIG. 12.

FIG. 14 is a side view of the unicondylar femoral implant of FIG. 12.

FIG. 15 is a top view of a tibial bone surface showing yet anotherembodiment of the present invention of tolerance profiles.

FIG. 16 is a top view of another embodiment of the present invention ofa prepared tibial bone.

FIG. 17 is a perspective view of a distal femur having a plurality ofplanar resections and a box cut with radiused edges.

FIG. 18A is a perspective view of one embodiment of a resected medialportion of a proximal tibia.

FIG. 18B is a front plan view of the resected medial portion shown inFIG. 18A.

FIG. 19A is a perspective view of another embodiment of a resectedmedial portion of a proximal tibia.

FIG. 19B is a front plan view of the a resected medial portion shown inFIG. 19A.

FIG. 20A is a perspective view of one embodiment of a resected portionon medial and lateral sides of a proximal tibia.

FIG. 20B is a front plan view of the resected portion on medial andlateral sides of a proximal tibia shown in FIG. 20A.

FIGS. 21A-24C show varying prepared keel slot depths in the proximaltibia.

FIG. 25A is a plan view of one embodiment of a keel punch.

FIG. 25B is a cross-section of the punch portion of the keel punch shownin FIG. 25A taken along line 2-2.

FIG. 26A is a cross-section of another embodiment of a punch portion ofa keel punch adjacent the proximal end of the punch portion.

FIG. 26B shows the difference in cross-section between a 3 mm burrstraight cut and the cross-section of the portion of the punch portionof the keel punch shown in FIG. 26A.

FIG. 26C shows the difference in cross-section between a 3 mm burr wavecut and the cross-section of the portion of the punch portion of thekeel punch shown in FIG. 26A.

FIG. 27A is an example of a cross-section of another embodiment of apunch portion of a keel punch adjacent the proximal end of the punchportion.

FIG. 27B is a cross-sectional view at Section 1-1 of FIG. 27A of a 2.5mm burr straight cut in relation to a major striation of the keel punchof FIG. 27A.

FIG. 27C is a cross-sectional view at Section 2-2 of FIG. 27A of the 2.5mm burr straight cut in relation to the minor striation of the keelpunch of FIG. 27A.

FIGS. 28A-28B are examples of a transverse cross-section of a tibialprosthesis keel, a punch portion of a keel punch, and a 2.5 mm burr wavecut.

FIGS. 29A-29B are examples of a transverse cross-section of a tibialprosthesis keel, a punch portion of a keel punch, and a 2.0 mm burr wavecut.

FIGS. 30A-30B are examples of a transverse cross-section of a tibialprosthesis keel, a punch portion of a keel punch, and a 2.0 mm burrdouble wave cut including a first wave cut and a second wave cut.

FIGS. 31A-31B are examples of a transverse cross-section of a tibialprosthesis keel, a punch portion of a keel punch, and successive 2.5 mmburr plunge cuts located at each major striation of tibial prosthesiskeel and a 1.5 mm burr straight cut.

FIGS. 32A-32C are examples of a transverse cross-section of a tibialprosthesis keel, a punch portion of a keel punch, and successive 2.5 mmburr plunge and drag cuts.

FIGS. 33A-33B are examples of a transverse cross-section of a tibialprosthesis keel, a punch portion of a keel punch, and successive 2.5 mmburr plunge cuts.

FIGS. 34A-34B are examples of a transverse cross-section of a tibialprosthesis keel, a punch portion of a keel punch, and successive 2.0 mmburr plunge cuts.

FIGS. 35A-35C are examples of a transverse cross-section of a tibialprosthesis keel, a punch portion of a keel punch, and successive 2.0 mmburr plunge diamond cuts each including first, second, third and forthplunge cuts.

FIG. 36A is a perspective view of a punch portion of a keel punch withsuccessive 2.5 mm drilled holes and 2.0 mm burr plunge cuts in betweeneach 2.5 mm drilled holes following the path of an outer perimetersurface of the punch portion.

FIGS. 36B-36C are examples of a transverse cross-section of the tibialprosthesis keel, the punch portion of the keel punch, and the 2.5 mmdrilled holes and 2.0 mm burr plunge cuts in between each 2.5 mm drilledholes.

FIG. 37A is a perspective view of a punch portion of a keel punch withsuccessive 2.5 mm drill pivot cuts following the path of an outerperimeter surface of the punch portion.

FIG. 37B is one embodiment of the angles between cuts in a 2.5 mm drillpivot cut.

FIGS. 37C-37D is an example of a transverse cross-section of the tibialprosthesis keel, the punch portion of the keel punch, and the 2.5 mmdrill pivot cuts.

FIG. 38A is a perspective view of an embodiment of a tibial prosthesiskeel having a custom keel shape around a portion of an outer perimeterthereof.

FIG. 38B is an embodiment of a 0.5° drafted end mill.

FIGS. 39A-39B are perspective views of the proximal tibia afterbicruciate retaining debulking and finishing is performed.

FIG. 39C shows a tibial implants having a keel and pegs configured to beretained within a slot machined into proximal tibia prepared surfaceshown in FIGS. 39A-39B.

FIGS. 40, 41 and 42 are perspective views of the distal femur afterdifferent debulking and finishing procedures are performed.

FIG. 43A is a side view and FIG. 43B is a plan view of an unicondylarprosthesis on the partial knee resurfacing region of FIG. 42.

FIG. 44A shows a distal femur including a tolerance profile or ribsextending along an anterior bone cut surface.

FIG. 44B shows a cross-sectional view of the ribs of FIG. 44A.

FIG. 45 shows a distal femur with an MMC implant profile.

FIG. 46 shows a distal femur with a LMC implant profile.

DETAILED DESCRIPTION

As used herein, the term “distal” means more distant from the heart andthe term “proximal” means closest to the heart. The term “inferior”means toward the feet and the term “superior” means towards the head.The term “anterior” means towards the front part of the body or the faceand the term “posterior” means towards the back of the body. The term“medial” means toward the midline of the body and the term “lateral”means away from the midline of the body.

FIG. 1 illustrates a perspective view of a tibial bone 10. Bone 10includes an unprepared region 11, a sagittal surface 15 and a transversesurface 20. Region 11 preferably retains unaltered or non-resectedpatient anatomy, which may include, for example, one or more of thefollowing: articular cartilage, meniscus, and anterior and posteriorcruciate ligament insertion regions. Sagittal surface 15 and transversesurface 20 represent cartilage/bone that have been prepared for anorthopedic procedure such as, for example, a partial knee resurfacing orunicondylar procedure. While many different types of prosthetic implantsmay be implanted on transverse surface 20, prosthetic implants disclosedin U.S. Ser. No. 61/500,257 titled “Prosthetic Implant and Method ofImplantation,” the priority of which was claimed in utility applicationpublished as U.S. Pat. Pub. No. 2012/0330429, now U.S. Pat. No.9,381,085, are particularly suited for implantation thereto thedisclosure of which is hereby incorporated by reference herein in itsentirety. In the embodiment shown, sagittal surface 15 has a generallyperpendicular angular relationship to transverse surface 20. An outerbone edge 16 extends from an anterior aspect 12 of sagittal surface 15to a posterior aspect 13 of sagittal surface 15, thus defining anouter-most edge 14 for transverse surface 20.

Transverse surface 20 is comprised of an anterior zone 21, an outer zone22, a posterior zone 23 and an internal zone 24. As shown, anterior zone21 is adjacent to sagittal surface 15, internal zone 24 and bone edge16. FIG. 2, which illustrates a top view of tibial bone 10, shows thatanterior zone 21 has generally linear contact geometry 25 with sagittalsurface 15 and non-linear contact geometries with bone edge 16 andinterior zone 24. Linear contact geometry 25 approximately occupiespreferably less than 33 percent of the outer profile of anterior zone24, as shown from this top view. In other embodiments, linear contactgeometry occupies between 10 and 50 percent of the outer profile ofanterior zone 24, and in other embodiments occupies less than 10 andmore than 50 percent of the outer profile of anterior zone 24.

As shown in FIGS. 1 and 2, both outer zone 22 and posterior zone 23 areadjacent to interior zone 24 and bone edge 16. Outer zone 22 is locatedalong bone edge 16 between anterior zone 21 and posterior zone 23;however, the majority of the area of outer zone 22 is shifted closertoward posterior zone 23. This posterior shift of zone 22 isfunctionally important because the contact region between a femoralunicondylar implant and tibial unicondylar implant is generally shiftedposteriorly throughout full range of leg motion. Outer zone 22 thereforemay be shifted posteriorly from its position as shown in FIG. 2.

As further shown in FIG. 2, anterior zone 21, outer zone 22 andposterior zone 23 comprise approximately 40 percent of the area oftransverse surface 20. Therefore, interior zone 24 comprisesapproximately 60 percent of the area of transverse surface 20. In otherembodiments, zones 21, 22 and 23 comprise more or less that 40 percentof the area of transverse surface 20, while zone 24 comprises more orless than 60 percent of the area of transverse surface 20. Further, therespective areas of anterior zone 21 and posterior zone 23 aresubstantially equivalent and greater than the area of outer zone 22. Inthe embodiment shown, the combination of the areas of anterior zone 21and posterior zone 23 occupy approximately 30 percent of the area oftransverse surface 20.

Anterior zone 21, outer zone 22 and posterior zone 23 have asubstantially equivalent surface texture, which is generally representedas a tolerance profile 30 as shown in FIG. 3. The three-dimensionalgeometry of tolerance profile 30 is the result of a rotational cuttingtool, such as a burr for example, making a plurality of channeledpreparations 31 into tibial bone 10. In the embodiment shown, theplurality of channeled preparations 31 follow a substantially linearpath. As shown in FIG. 4, tolerance profile 30 has a height 32, a width36 and a plurality of protrusions 33. Height 32 is essentially thedistance from the most distal bone preparation 34 made with the cuttingtool to the highest relative peak 35 of the bone. In other words, height32 may be described as the planar distance between peak 35 and trough 34of one of the channeled preparations 31. Tolerance profile 30 ispreferably designed to be very accurate, or “tight”. Therefore, height32 for all protrusions 33 are substantially consistent from protrusions33 to adjacent protrusion 33.

Width 36 of the plurality of channel preparations 31 is defined as thedistance from bone peak 35 to adjacent peak 35 in a transversedirection. Similar to the accuracy requirements for height 32, width 36is designed to be consistent and accurate within respective zones 21, 22and 23. Further, the tolerance profile 30, including the distal bonepreparation 34 to peak 35 distance, must be substantially equivalentrelative to anterior zone 21, outer zone 22 and posterior zone 23.Alternately described, the proximal-distal location relative tibial bone30 must be accurate for respective zones 21, 22 and 23.

Interior zone 24 has a tolerance profile 40, also illustrated in FIGS. 3and 4. The three-dimensional geometry of tolerance profile 40 is theresult of a rotational cutting tool, such as a burr, making a pluralityof channeled preparations 41 which follow substantially linear paths. Inthis embodiment, the same rotational cutting tool is used to preparetolerance profile 30 and tolerance profile 40. Tolerance profile 40 hasa height 42 as measured from the most distal bone preparation 44 to thehighest relative peak 35 for a plurality of protrusions 43. In otherwords, height 42 may be described as the planar distance between peak 45and trough 44 of one of the channeled preparations 41. Tolerance profile40 also has a width 46 as measured from peak 35 to adjacent peak 35 in atransverse direction. Tolerance profile 40 is not required to be asaccurate, or “tight”, as the tolerance profile 30 for zones 21, 22 and23. As show in FIGS. 3 and 4, tolerance profile 30 has a densercross-section than that of the cross-section of tolerance profile 40.

Alternately described, height 42 and width 46 of profile 40 are largerthan height 33 and width 36 of profile 30. Further, there is a lesserrequirement for consistency from protrusion 43 to protrusion 43 forprofile 40 that for the respective protrusion 33 to protrusion 33consistency in profile 30. Simply stated, the preparation for interiorzone 24 may be performed faster, with less rotational instrument passesacross the bone, and with less accuracy than for anterior zone 21, outerzone 22 and posterior zone 23.

The cartilage and/or bone of tibial bone 10 may be prepared with theassistance of a robot. Robot assisted bone preparation may include:implant specific software, saw cutting, milling/burring or otherrotational cutting instruments and various levels of surgeon interface.For example, in a first robot mode, the robot may perform thecartilage/bone preparation with the surgeon observing. In such a mode,the surgeon may not have any control over the movement of the robot ormay instead be controlling the movement of the robot remotely. In asecond robot mode, the surgeon may actually guide a rotational cuttingtool within a predetermined boundary. In the second mode, the implantspecific software is preferably programmed within the robot, whichestablishes boundary constraints for the preparation. Here, the surgeonwill not be able to extend the preparation outside of a specificboundary. For the bone preparation shown, the surgeon preferably uses acombination of both the first and second robot modes and uses a burr asthe cutting tool. In both the first and second robot modes, the surgeonwould be able to stop the robotic preparation if necessary. Such robotictechnology that may be applied for use with the present inventionincludes that described in U.S. Pat. Nos. 6,676,669, 7,892,243,6,702,805, and 6,723,106 as well as U.S. Patent Application Nos.2010/0268249, 2008/0202274, 2010/0268250, 2010/0275718, and2003/0005786, the disclosures of which are all hereby incorporated byreference in their entireties.

Once the bone is prepared as previously described, the prosthetic tibialimplant 50, shown in FIG. 5, may be implanted on the prepared bonesurface. Implant 50 is a modular style, unicondylar design that has aproximal surface 51 and a distal surface 52. The modular style indicatesthat a separate polyethylene insert (not shown) is assembled to proximalsurface 51. Distal surface 52 is designed for cemented or cementlessfixation to the bone and includes a porous ingrowth/ongrowth structuresuch as beads or a porous metal structure. An example of a beadedingrowth structure is described in U.S. Pat. No. 4,550,448, thedisclosure of which is hereby incorporated by reference herein in itsentirety. The porous metal structure may be manufactured from thetechnology described in U.S. Pat. No. 7,537,664, U.S. Patent ApplicationNo. 2006/0147332, U.S. Pat. No. 7,674,426, U.S. Patent Application No.2006/0228247 and U.S. Pat. No. 7,458,991, the disclosures of which areall hereby incorporated by reference in their entireties.

Implant 50 is implanted onto tibial bone 10 by initially contactingpeaks 35 of anterior zone 21, outer zone 22 and posterior zone 23. Afterimplant 50 has established contact, a force is applied to proximalsurface 51. The applied force results in the compaction of the pluralityof protrusions 33 until the implant reaches the final seating locationon distal bone preparation 34. The compaction of bone preferably has animproved biologic effect on the biologic ingrowth/ongrowth process. Whenimplant 50 is seated in a final location, the implant is preferablycontacting anterior zone 21, outer zone 22, posterior zone 23 andsagittal surface 15. Contact with respect zones 21, 22 and 23 preferablyresults in an accurate and stable surface for the implant 50 because ofthe accuracy of tolerance profile 30. In the embodiment shown, implant50 is not in contact with interior zone 24; however, the distancebetween distal surface 52 and peaks 45 will be at a distance conduciveto future bone ingrowth/ongrowth.

FIG. 6 shows an alternate embodiment of a prepared tibial bone 110having a transverse surface 120 including an anterior zone 121, an outerzone 122, a posterior zone 123, an interior zone 124, a sagittal surface115 and a bone edge 116. Both anterior zone 121 and posterior zone 123are adjacent to sagittal surface 115, bone edge 116 and interior zone124. While sagittal surface 115 may have a substantially perpendicularrelationship with transverse surface 120, surface 115 may also have anon-perpendicular relationship with surface 120. Outer zone 122 ispreferably adjacent to both interior zone 124 and bone edge 116. Thegeometry for zones 121, 122, 123 and 124 may be any combination oflinear or non-linear geometries as previously described. It isunderstood that each zone may have a unique geometry, or alternatively,each zone may have zone geometries that are substantially similar, orany other combination thereof. In the embodiment shown, respective zones121, 122 and 123 occupy approximately 50 percent of prepared transversesurface 120. Therefore, interior zone 124 also occupies approximately 50percent of prepared transverse 120. In other embodiments, zones 121, 122and 123 comprise more or less that 50 percent of the area of transversesurface 120, while zone 124 comprises more or less than 50 percent ofthe area of transverse surface 120. As shown, the percent area ofcoverage is substantially equivalent for zones 121, 122 and 123. Anytolerance profiles are consistent with that previously described for allzones.

In yet other embodiments, which are not shown, the range of coverage forthe combination of the anterior zone, outer zone and posterior zone mayrange between 10 and 90 percent. In still yet other embodiments, therange or coverage for the combination of the anterior, outer andposterior zones may be less than 10 percent or more than 90 percent.Further, the range of coverage for the anterior zone, outer zone,posterior zone may be substantially similar, different, or anycombination thereof. In all embodiments, the tolerance profiles areconsistent with that previously described for all zones.

FIG. 7 shows a perspective view of an alternate embodiment of thegeometry of a tolerance profile 130 that may be applied to any of theanterior, outer, posterior or interior zones previously described. Here,the three dimensional geometry of tolerance profile 130 is essentially asinusoidal or pyramid-like pattern consisting of a plurality of peaks135 and plurality of distal bone preparations 134. A cross-sectionalside view of the preparation is illustrated in FIG. 8. Regarding FIGS. 7and 8, the geometry may be accomplished by a series of generally linearpasses of a rotational cutting instrument, followed by a series ofgenerally orthogonal rotational cutting instrument passes. In anotherembodiment, the relationship between cutting instrument passes may be ata non-orthogonal angle. In yet other embodiments, the cutting path forthe rotational cutting instrument may be circular, or any othernon-linear path, or any combination of linear and non-linear paths.

FIG. 9 shows a cross-sectional view of another embodiment of thegeometry of a tolerance profile for any of, or any combination oftolerance profiles for anterior, outer, posterior or interior zones.Here, the general shape of protrusions 233 is substantially rectangular.It is envisioned that in yet other embodiments, a rotational cuttingtool may take multiple cutting paths resulting in many geometricalshapes such as circular, square, trapezoid or any other linear ornon-linear geometries.

FIG. 10 illustrates a view of the distal aspect of a femoral bone 310and FIG. 11 illustrates a view of the posterior aspect of femoral bone310. Here, femoral bone 310 has been prepared to receive a unicondylarfemoral implant (not shown). Consistent with that previously described,the bone is prepared using a rotational cutting tool guided by asurgeon, robot, or combination thereof. Femoral bone 310 includes ananterior zone 321, an outer zone 322, a posterior zone 323 and aninterior zone. Zones 321, 322 and 323 share a substantially similartolerance profile 330 (not shown). Interior zone 324 has a toleranceprofile 340 (not shown) which is different than profile 330. Profile 330is designed as a more accurate and “tighter” tolerance compared withprofile 340. The methods of implantation are also consistent with thatpreviously described.

FIGS. 12-14 illustrate an embodiment of a unicondylar femoral component400 having an articular surface 420 and a bone contacting surface 424.Here, the implant includes an anterior zone 421, an outer zone 422 and aposterior zone 423 designed to mate with the prepared femoral bone, suchas previously described. Zones 421, 422 and 423 may have any geometry,or combination of geometries such as: spherical indentations, generallycylindrical indentations, sinusoidal, or other geometry. The concept isthat zones 421, 422 and 423 would be manufactured with a tighter degreeof tolerance as compared with other aspects of the implant. Further, thespecific geometry of these respective zones is designed to improvesecure initial fixation to the prepared bone surface and promoteingrowth/ongrowth.

Another aspect of the present invention is to apply a bone adhesive tothe interior zone of the bone preparation or to an interior zone of animplant component. An example of a medical adhesive is described in U.S.Patent Application Nos. 2009/0318584, 2009/0280179, and 2010/0121459,the disclosures of which are hereby incorporated by reference herein intheir entirety. In this aspect of the present invention, the boneadhesive would provide initial fixation to an interior zone, which isprepared to a larger tolerance profile, but will preferably resorb overtime allowing for bone ingrowth/ongrowth.

FIG. 15 shows a prepared tibial bone surface with an alternate toleranceprofile pattern. Here, tibial bone has an anterior end 501, a posteriorend 502, a sagittal surface 515 and an outer edge 516. The bone isprepared to three different tolerance zones: peripheral zone 521,posterior zone 522 and anterior zone 523. These three tolerance zonesare each prepared to different levels of tolerance accuracy. Forexample, peripheral zone 521 is prepared to be the more accurate zone ofthe three tolerance zones. Anterior zone 523 is prepared to be the leastaccurate tolerance zone and has a surface area percentage less thananterior zone 523. Posterior zone 522 has an accuracy ranging betweenrespective zones 521 and 523. As a specific example, peripheral zone 521has a tolerance of ±0.010 in, posterior zone 522 has a tolerance of+0.010/−0.025 in, and anterior zone 523 has a tolerance of ±0.025 in.

The known anatomy of the proximal end of a tibial bone is that theperiphery, or outer region, of the bone is cortical bone and theinterior regions are cancellous bone. Regions of the cancellous bone mayhave different densities. For example, the cancellous bone in theposterior regions of the proximal tibial may be denser than bone in theanterior region of the cancellous bone. This may be the result ofincreased loading of this region of the proximal tibia, and via wolf'slaw, bone is remodeled in response to the increased loading.

Tolerance zones 521, 522 and 523 of FIG. 15 are now further describedwith respect to the anatomy of a proximal tibial bone 500. Peripheralzone 521 substantially covers cortical bone which extends along outeredge 516. In this embodiment, peripheral zone 521 is also substantiallyadjacent to sagittal surface 515. Posterior zone 522 substantiallycovers a region of dense cancellous bone compared to the cancellous bonecovered by region 523. Zones 522 and 523 are in part adjacent toperipheral zone 521. The density of the cancellous bone of a patient bybe determined preoperatively by MRI, CT, DEXA or other know scanningmeans. Alternately, the density of the bone may be determinedinteroperatively using a known scanning means, visually by the surgeonor through physical surgeon contact.

FIG. 16 illustrates a top view of an alternate embodiment of a preparedtibial bone 600. Bone 600 has an anterior end 601, a posterior end 602,a sagittal surface 615 and an outer edge 616. Bone 600 has threetolerance zones: a peripheral zone 621, a posterior zone 622 and ananterior zone 623. Peripheral zone 621 extends along outer edge 616 andsubstantially covers the cortical bone region of bone 600. Posteriorzone 621 substantially covers a region of dense cancellous bone comparedto the cancellous bone covered by region 623. Here, zones 622 and 623are adjacent to sagittal surface 515.

In alternate embodiments of tibial bone 500 and bone 600, any of thepreviously describe combinations of limitations may be utilized. Forexample, the relationship of surface area coverage may vary betweentolerance zones. Also, the accuracy of tolerance preparation may rangefrom ±0.001 to ±0.100, and include any combination of tolerancestherein. In yet alternate embodiments, posterior zone 522 or 622, maysubstantially cover an area of dense cancellous bone and besubstantially surrounded by a less accurate tolerance zone, 523 or 623respectively.

In all embodiments described above, there was an anterior zone, outerzone and posterior zone which are held to a more accurate, or “tighter,”tolerance than an interior zone. In alternate embodiments, there may beless than three zones held to a more accurate tolerance profile. In yetother embodiments, there may be more than three zones held to a moreaccurate tolerance profile.

Conventional instruments used in orthopaedic surgeries often include theuse of sawblades, punches, and chisels that have many limitations. Forexample, surgeons often over-prepare or leave sharp corners in boneusing these conventional instruments as a result of the dimensionsthereof. Further, the geometry of the resected bone using theseconventional instruments is generally the result of the skill andaccuracy of the surgery.

The following embodiments that will be described herein use a burr toolhaving a certain diameter and robotic technology to prepare bone withmore accuracy and control. Surgeons using these tools will no longer belimited to making planar resections with standard alignmentinstrumentation or punches and chisels to remove bone. By using a burrtool, the robot can prepare bone to any preoperatively planned shape orintraoperatively desired shape based on the capabilities of the robot.For example, the burr tool can be used to cut radiused edges to adesired tolerance, as opposed to sharp corners that generally resultfrom surgeries using conventional instrumentation.

FIG. 17 is a perspective view of a distal femur 700 having a pluralityof planar resections 702. Such planar resections are generally referredto as distal, anterior, posterior, and anterior and posterior chamfercuts. A burr having a certain diameter was used to create radiusedcorners 704, 706 along inner edges 708 of the resected femur bone. Inneredges 708 with radiused corners 704, 706 correspond to the dimensions ofa box of a posterior-stabilized femoral component. The radius of theradiused corners 704, 706 substantially match the radius of thefinishing cutter that is used to make the resection.

FIG. 18A is a perspective view of proximal tibia 720 having a resectedmedial portion 722. The resected medial portion 722 preferably houses atleast a portion of an implant that is configured to engage an articularsurface of a unicondylar or bi-compartmental femoral implant, forexample. The resected medial portion has a radiused corner 724 at theintersection of a transverse wall 725 and a sagittal wall 726 adjacentthe tibial eminence as shown in FIG. 18B. Preferably, the radius of theradiused corner 724 substantially matches the radius of the finishingcutter that is used to make the resection.

FIG. 19A is a perspective view of proximal tibia 740 having a resectedmedial portion 742. The resected medial portion has a radiused corner744 at the intersection of a transverse wall 745 and a sagittal wall 746adjacent the tibial eminence as shown in FIG. 19B. Radiused corner 744runs deeper along sagittal wall 746 than radiused corner 724 shown inFIGS. 18A-B. The radius of the radiused corner 744 substantially matchesthe radius of the finishing cutter that is used to make the resection;however, the radius of the radius corner 744 may be larger than theradius of the finishing cutter. In such a case, the finishing cutter maymake more than one pass in order to create the dimensions of resectedradiused corner 744.

FIG. 20A is a perspective view of proximal tibia 760 having a resectedportion 762 on medial and lateral sides thereof. Resected portion 762 isformed around the tibial eminence resulting in a tibial plateau 764. Theresected portion has radiused corners 767, 768 at the intersection of atransverse wall 765 and a sagittal wall 766 adjacent the tibial eminenceas shown in FIG. 20B. The tibial eminence is not resected so as topreserve the anterior and poster cruciate ligaments in a kneearthroplasty procedure. A burr is preferably used to resect a curvedrecess 770 in the tibial plateau 764. A portion of a correspondingbicruciate retaining implant is configured to engage and be housed atleast partially within curved recess 770.

For cementless tibial keel preparation, an interference fit between thetibia and the implant is desired to achieve fixation. The level ofinterference can preferably be customized using a robot. Preferably, therobot will machine a slot in the tibia, into which a tray will beimpacted, and the depth and width of the slot can be tailored to achievea desired level of interference. For example, a keel slot can beprepared to the full depth of a baseplate keel or to a partial depth toachieve greater interference and pressfit if desired.

For cemented tibial keel preparation, surgeons generally want to ensurethere is adequate cement mantle around a tibial baseplate to achieveproper fixation. Using the robot, the size of the cement mantle can becustomized by tuning in a desired depth and width of a keel slot.

FIGS. 21A-24C show varying prepared keel slot depths in the proximaltibia. The lesser the depth of the keel slot the greater theinterference and pressfit there will be on the baseplate keel of tibialprosthesis when the baseplate keel is inserted into the prepared keelslot and into cancellous bone. The depth of keel slot preparation may bedefined as the length of the keel slot from a transverse resection onproximal tibia to an end portion thereof within the tibial shaftmeasured in a superior to inferior direction, for example.

Sclerotic bone may be found at the outskirts of the width of thebaseplate keel of the tibial prosthesis approximately 10-14 mm from thetransverse resection of the proximal tibia. Preferably, programming ofthe robot burr should prepare all of this region to get beyond thesclerotic bone. There is a general desire for quick tibial keelpreparation and the shallower the keel preparation, the quicker thispart of a procedure will be. Further, with shallower keel preparationthere are generally less restrictions on the cutter geometry such asheat generation and debris relief, for example.

FIGS. 21A and 21B are perspective views of a shallow keel slot 802 in aproximal tibia 800. Keel slot 802 includes a central portion 804 flankedby two wing portions 806, 808. As shown in FIG. 21C, keel slot 802 isdeeper adjacent the ends of the two wing portions 806, 808 and isshallower in a central region 810. The deeper portions of keel slot 802are preferably curved forming curved portions 807, 809 while the centralregion 810 is preferably straight. Keel slot 802 is preferably formed bya 2.5 mm burr while a smaller or larger diameter burr may be used. Thedepth of the keel slot is approximately ¼ the length of the baseplatekeel of the tibia prosthesis that will be implanted in and through thekeel slot 802. The depth is measured preferably as a linear distance D1from the proximal tibia surface 812 to a line tangent to the curvedportions 807, 809 of the keel slot 802. The max depth of keel slot 802is preferably 10.2 mm (0.4 in).

FIGS. 22A and 22B are perspective views of a deeper keel slot 822 in aproximal tibia 820. Keel slot 822 includes a central portion 824 flankedby two wing portions 826, 828. As shown in FIG. 22C, keel slot 822 isdeeper adjacent the ends of the two wing portions 826, 828 and isshallower in a central region 830. The deeper portions of the keel slotare preferably curved forming curved portions 827, 829 while the centralregion 830 is preferably straight. Central region 830 is more prominentthat central region 810 of keel slot 802. Keel slot 822 is preferablyformed by a 2.5 mm burr while a smaller or larger diameter burr may beused. The depth of keel slot 822 is approximately ½ the length of thebaseplate keel of the tibia prosthesis that will be implanted in andthrough the keel slot 822. The depth is measured preferably as a lineardistance D2 from the proximal tibia surface 822 to a line tangent to thecurved portions 827, 829 of the keel slot 822. The max depth of keelslot 822 is preferably 14 mm (0.55 in).

FIGS. 23A and 23B are perspective views of an even deeper keel slot 842in a proximal tibia 840. Keel slot 842 includes a central portion 844flanked by two wing portions 846, 848. As shown in FIG. 23C, keel slot842 is shallower adjacent the ends of the two wing portions 846, 848 andis deeper in a central region 850. The shallower portions of keel slot842 are preferably curved forming curved portions 847, 849 as well ascentral region 850. Central region 850 is preferably formed with alead-in central opening. Keel slot 842 is preferably formed by a 2.5 mmburr while a smaller or larger diameter burr may be used. The depth ofkeel slot 842 is approximately ¾ the length of the baseplate keel of thetibia prosthesis that will be implanted in and through the keel slot842. The depth is measured preferably as a linear distance D3 from theproximal tibia surface 842 to a line tangent to the central region 850of the keel slot 842. The max depth of keel 842 is preferably 23 mm (0.9in).

FIGS. 24A and 24B are perspective views of an even deeper keel slot 862in a proximal tibia 860 that the keel slot 842 in proximal tibia 840.Keel slot 862 includes a central portion 864 flanked by two wingportions 866, 868. As shown in FIG. 24C, keel slot 862 is shalloweradjacent the ends of the two wing portions 866, 868 and is deeper in acentral region 870. The shallower portions of keel slot 862 arepreferably curved forming curved portions 867, 869 as well as centralregion 870. Keel slot 862 is preferably formed by a 2.5 mm burr while asmaller or larger diameter burr may be used. The depth of keel slot 862is approximately the full length of the baseplate keel of the tibiaprosthesis that will be implanted in and through the keel slot 862. Thedepth is measured preferably as a linear distance D4 from the proximaltibia surface 862 to a line tangent to the central region 870 of thekeel slot 862. The max depth of keel slot 862 is preferably 33.5 mm(1.32 in).

FIG. 25A is a plan view of one embodiment of a keel punch 900. Keelpunch 900 includes a head portion 902, a shaft portion 904 and a punchportion 906. A distal portion 908 of punch portion 906 is received in aprepared keel slot through the proximal tibia and into cancellous boneuntil a proximal portion 910 of punch portion 906 is approximately 0.09″from a resected transverse surface on the proximal tibia. A centrallongitudinal axis of shaft portion 904 is preferably angled 1° from acentral longitudinal axis of punch portion 906.

The cross-section of punch portion 900 as shown in section 2-2 of FIG.25B is substantially similar to the keel slots shown in FIG. 21A-24C.Punch portion 906 includes a central portion 912 flanked by two wingportions 914, 916. As shown in FIG. 25B, the cross-section of punchportion 900 shows striations 918 of punch portion 906 adjacent theproximal portion 910 of punch portion 906. Punch portion 906 includes aplurality of striations 918 which are peak portions along thecross-section of the wing portions 914, 916 of punch portion 906. Theplurality of striations 918 are flanked by valley portions 920.Striations 918 are configured to form an interference fit with the boneof the proximal tibia while valley portions 920 are configured to formrelief portions that may either be clearance or interference portions.

A traditional keel punch as shown in FIG. 25A, for example, leaves akeel slot adjacent the transverse surface of the proximal tibia having across-section generally as shown in FIG. 25B, for example. Thecross-section as shown in FIG. 25B may be modified using a burr having aparticular diameter following a particular tool path. The followingembodiments discuss the different levels of clearance and interferencebetween certain burr sizes and tool paths used to create a keel slot inthe proximal tibia.

FIG. 26A is an example of a cross-section 1000 of a punch portion of akeel punch adjacent the proximal end of the punch portion. FIG. 26Bshows the difference in cross-section between a 3 mm burr straight cut1010 and the cross-section 1000 of a portion of the punch portion of thekeel punch shown in FIG. 26A. The 3 mm burr straight cut 1010 providesapproximately 0.0035″ clearance with a tibial prosthesis, which providesless interferences with the tibial prosthesis compared to conventionaltibial resection using the keel punch. FIG. 26C shows the difference incross-section between a 3 mm burr wave cut 1020 and the cross-section1000 of a portion of the punch portion of the keel punch shown in FIG.26A. The 3 mm burr wave cut 1020 follows the direction of the arrows inalternating posterior and anterior directions. The 3 mm burr wave 1020cut provides approximately 0.011″ clearances and 0.004″ interferences ata minimum with the tibial prosthesis, which provides greater clearancesand lesser interferences with the tibial prosthesis compared to 3 mmburr straight cut 1010 shown in FIG. 26B.

FIG. 27A is an example of a cross-section 1100 of a punch portion of akeel punch adjacent the proximal end of the punch portion. FIG. 27A alsoshows a 2.5 mm burr straight cut 1110 overlay on cross-section 1100. Thepunch portion of the keel punch shown includes a plurality ofalternating major striations 1102 and minor striations 1104 and theinterference and clearance differences at the locations of the major andminor striations in relation to a conventional keel punch. As explainedabove, major and minor striations 1102, 1104 are alternating peaks andvalley portions, respectively. Major striations 1102 are portions on thepunch portion of the keel punch that provide relatively greaterinterference with a corresponding keel of a tibial prosthesis than areprovided by minor striations 1104, if at all. For instance, majorstriations 1102 generally provide interference with a corresponding keelof a tibial prosthesis, while minor striations 1104 generally provide nointerference, but instead provide clearance with a corresponding keel ofa tibial prosthesis.

As shown in FIG. 27B, there is a cross-sectional view at Section 1-1 ofFIG. 27A of the 2.5 mm burr straight cut 1110 in relation to the majorstriation 1102 of the conventional keel punch. There is an added 0.007″interference difference created with the 2.5 mm burr straight cut 1110in relation to the interference created by the major striation 1102 ofthe conventional keel punch at Section 1-1. Using the 2.5 mm burrstraight cut 1110, there will result in greater interferences with thekeel of the tibial prosthesis at the major striations thereof comparedto the resulting interferences created with convention keel punchpreparation. FIG. 27C there is a cross-sectional view at Section 2-2 ofFIG. 27A of the 2.5 mm burr straight cut 1110 in relation to the minorstriation 1104 of the conventional keel punch. As shown, there is a0.012″ clearance difference created between the 2.5 mm burr straight cut1110 in relation to the clearance created by the minor striation 1104 ofthe conventional keel punch at Section 2-2. Using the 2.5 mm burrstraight cut 1110, there will result in lesser clearances (i.e. greaterinterferences) with the keel of the tibial prosthesis at the minorstriations thereof compared to the resulting clearances created withconventional keel punch preparation.

FIG. 28A is an example of a transverse cross-section 1200 of a tibialprosthesis keel 1220, a punch portion 1240 of a keel punch, and a 2.5 mmburr wave cut 1260. FIG. 28A shows the differences in interferences andclearances created between each of the punch portion 1240 and 2.5 mmburr wave cut 1260 in relation to the tibial prosthesis keel 1220. FIG.28B shows that the 2.5 mm burr wave cut 1260 results in alternating0.014″ and 0.028″ interferences between alternating peaks 1264 andvalleys 1262 of the 2.5 mm burr wave cut 1260, respectively, in relationto alternating major striations 1224 of the tibial prosthesis keel 1220.Further, the 2.5 mm burr wave cut 1260 results in less than a 0.002″interference between an intermediate portion 1263 of the 2.5 mm burrwave cut 1260 located between the alternating peaks 1264 and valleys1262 thereof and the minor striations 1224 of the tibial prosthesis keel1220.

FIG. 29A is an example of a transverse cross-section 1300 of a tibialprosthesis keel 1320, a punch portion 1340 of a keel punch, and a 2.0 mmburr wave cut 1360. FIG. 29A shows the differences in interferences andclearances created between each of the punch portion 1340 and 2.0 mmburr wave cut 1360 in relation to the tibial prosthesis keel 1320. FIG.29B shows that the 2.0 mm burr wave cut 1360 results in alternating0.014″ and 0.048″ interferences between alternating peaks 1364 andvalleys 1362 of the 2.0 mm burr wave cut 1360, respectively, in relationto alternating major striations 1324 of the tibial prosthesis keel 1320.Further, the 2.0 mm burr wave cut 1360 results in less than a 0.002″interference between an intermediate portion 1363 of the 2.0 mm burrwave cut 1360 located between the alternating peaks 1364 and valleys1362 thereof and the minor striations 1324 of the tibial prosthesis keel1320.

FIG. 30A is an example of a transverse cross-section 1400 of a tibialprosthesis keel 1420, a punch portion 1440 of a keel punch, and a 2.0 mmburr double wave cut 1460 including a first wave cut 1461 and a secondwave cut 1463. First and second wave cuts 1461, 1463 travel along thelength of each cut in alternating anterior and posterior directions.FIG. 30A shows the differences in interferences and clearances createdbetween each of the punch portion 1440 and 2.0 mm burr double wave cut1460 in relation to the tibial prosthesis keel 1420. FIG. 30B shows thatthe 2.0 mm burr double wave cut 1460 results in alternating 0.014″ and0.012″ interferences between alternating peaks 1464 and valleys 1462 ofthe 2.0 mm burr double wave cut 1460, respectively, in relation toalternating major striations 1424 and minor striations 1422 of thetibial prosthesis keel 1420, respectively.

FIG. 31A is an example of a transverse cross-section 1500 of a tibialprosthesis keel 1520, a punch portion 1540 of a keel punch, andsuccessive 2.5 mm burr plunge cuts 1560 located at each major striation1524 of tibial prosthesis keel 1520 and a 1.5 mm burr straight cut 1580.FIG. 31A shows the differences in interferences and clearances createdbetween each of the punch portion 1540 and successive 2.5 mm burr plungecuts 1560 located at each major striation 1524 of tibial prosthesis keel1520 and a 1.5 mm burr straight cut 1580 in relation to the tibialprosthesis keel 1520. FIG. 31B shows that the successive 2.5 mm burrplunge cuts 1560 located at each major striation 1524 of tibialprosthesis keel 1520 result in a 0.021″ interference with each majorstriation 1524 of tibial prosthesis keel 1520. Also shown in FIG. 31B isthat at each minor striation 1522 of tibial prosthesis keel 1520 thereis a 0.023″ interference with the 1.5 mm burr straight cut 1580.

FIG. 32A is an example of a transverse cross-section 1600 of a tibialprosthesis keel 1620, a punch portion 1640 of a keel punch, andsuccessive 2.5 mm burr plunge and drag cuts 1660. A central axis of theplunge of the 2.5 mm burr is preferably located adjacent an intermediateportion 1623 thereof located between an adjacent minor striation 1622and major striation 1624 of the tibial prosthesis keel 1620. The lengthof the drag of the 2.5 mm burr in a medial to lateral direction (or viceversa depending on whether the left or right tibia is being resected) isthe distance between adjacent intermediate portions 1623 along thelength of the tibial prosthesis keel 1620. FIG. 31A shows thedifferences in interferences and clearances created between each of thesuccessive 2.5 mm burr plunge and drag cuts 1660 in relation to thetibial prosthesis keel 1520. FIG. 32B shows that the maximuminterference between the minimum striation 1662 created betweensuccessive 2.5 mm burr plunge and drag cuts 1660 and the minor striation1622 of the tibial prosthesis keel 1620 is 0.052″ (depending on amountof plunge overlap between successive 2.5 mm burr plunge and drag cuts1660). FIG. 32C shows that the minimum interference between the maximumstriation 1664 created between successive 2.5 mm burr plunge and dragcuts 1660 and the maximum striation 1624 of the tibial prosthesis keel1620 is 0.021″.

FIG. 33A is an example of a transverse cross-section 1700 of a tibialprosthesis keel 1720, a punch portion 1740 of a keel punch, andsuccessive 2.5 mm burr plunge cuts 1760. A central axis of each of thesuccessive 2.5 mm burr plunge cuts 1760 is preferably located adjacentan intermediate portion 1723 located between an adjacent minor striation1722 and major striation 1724 of the tibial prosthesis keel 1720.Successive central axes of 2.5 mm burr plunge cuts 1760 are preferablyat least 0.065″ apart from one another. FIG. 33A shows the differencesin interferences and clearances created between each of the punchportion 1740 and successive 2.5 mm burr plunge cuts 1760 in relation tothe tibial prosthesis keel 1720. FIG. 33B shows that the successive 2.5mm burr plunge cuts 1760 located at a major striation 1724 of tibialprosthesis keel 1720 results in a maximum 0.037″ interference with aminor striation 1764 of the successive 2.5 mm burr plunge cuts 1760.Also shown in FIG. 33B is that minor striations 1722 of tibialprosthesis keel 1720 there is a minimum 0.003″ interference with a majorstriation 1762 of the successive 2.5 mm burr plunge cuts 1760.

FIG. 34A is an example of a transverse cross-section 1800 of a tibialprosthesis keel 1820, a punch portion 1840 of a keel punch, andsuccessive 2.0 mm burr plunge cuts 1860. A central axis of each of thesuccessive 2.0 mm burr plunge cuts 1860 is preferably located adjacentan intermediate portion 1823 located between an adjacent minor striation1822 and major striation 1824 of the tibial prosthesis keel 1820.Successive central axes of 2.0 mm burr plunge cuts 1860 are preferablyat least 0.030″ apart from one another. FIG. 34A shows the differencesin interferences and clearances created between each of the punchportion 1840 and successive 2.0 mm burr plunge cuts 1860 in relation tothe tibial prosthesis keel 1820. FIG. 34B shows that the successive 2.0mm burr plunge cuts 1860 located at a major striation 1824 of tibialprosthesis keel 1820 results in a maximum 0.055″ interference with aminor striation 1864 of the successive 2.0 mm burr plunge cuts 1860.Also shown in FIG. 34B is that minor striations 1822 of tibialprosthesis keel 1820 there is a minimum 0.013″ interference with a majorstriation 1862 of the successive 2.0 mm burr plunge cuts 1860.

FIG. 35A is an example of a transverse cross-section 1900 of a tibialprosthesis keel 1920, a punch portion 1940 of a keel punch, andsuccessive 2.0 mm burr plunge diamond cuts 1960 including first, second,third and forth plunge cuts 1966, 1967, 1968 and 1969, respectively. Acentral axis of first plunge cut 1966 of the 2.0 mm burr for eachdiamond cut is preferably located adjacent an intermediate portion 1923located between an adjacent minor striation 1922 and major striation1924 of the tibial prosthesis keel 1920. The second, third and forthplunge cuts are then created in a clockwise or counterclockwise fashionfrom first plunge cut 1966. FIGS. 35B and 35C show the differences ininterferences and clearances created between each of the successive 2.0mm burr plunge diamond cuts 1960 in relation to the tibial prosthesiskeel 1620. FIG. 35B shows that the maximum interference between theminimum striation 1962 created between successive 2.0 mm burr plungediamond cuts 1960 and the minor striation 1922 of the tibial prosthesiskeel 1920 is 0.052″ (depending on amount of plunge overlap betweensuccessive 2.0 mm burr plunge diamond cuts 1960). FIG. 35C shows thatthe minimum interference between the maximum striation 1964 createdbetween successive 2.0 mm burr plunge diamond cuts 1960 and the maximumstriation 1924 of the tibial prosthesis keel 1920 is 0.013″.

FIG. 36A is a perspective view of a punch portion 2040 of a keel punchwith successive 2.5 mm drilled holes 2060 and 2.0 mm burr plunge cuts2070 in between each 2.5 mm drilled holes 2060 following the path of anouter perimeter surface 2042 of the punch portion. The depth of the 2 mmburr plunge cuts 2070 preferably are at a constant offset ofapproximately 8 mm from the outer perimeter surface 2042 of the punchportion. This offset allows for bone compression and interference when atibial prosthesis keel 2020 is fully received in the prepared resectionusing this multi-cut strategy. FIG. 36B is an example of a transversecross-section 2000 of the tibial prosthesis keel 2020, the punch portion2040 of the keel punch, and the 2.5 mm drilled holes 2060 and 2.0 mmburr plunge cuts 2070 in between each 2.5 mm drilled holes 2060. Acentral axis of each of the successive 2.5 mm drilled holes 2060 ispreferably located adjacent a major striation 2024 of the tibialprosthesis keel 2020. FIG. 36C shows that the successive 2.5 mm drilledholes 2060 located adjacent major striations 2024 of tibial prosthesiskeel 2020 result in approximately 0.021″ interference with a majorstriation 2064 of the successive 2.5 mm drilled holes 2060. Also shownin FIG. 36B is that minor striations 2022 of tibial prosthesis keel 2020there is approximately 0.013″ interference created between a minorstriation 2062 of the 2 mm burr plunge cuts 2060.

FIG. 37A is a perspective view of a punch portion 2140 of a keel punchwith successive 2.5 mm drill pivot cuts 2160 following the path of anouter perimeter surface 2142 of the punch portion. The 2.5 mm drillshown in FIG. 37B removes material in the proximal tibia by pivoting ona point fixed at a distal end of the desired depth following what wouldbe the outer perimeter surface 2142 of the punch portion. Each pivot cutincludes three separate plunge cuts having an axis approximately 10°from each successive plunge. Each successive plunge cut can be more orless than 10° depending on the interference desired between theresection created and a corresponding tibial prosthesis keel such asprosthesis keel 2120. FIG. 37C is an example of a transversecross-section 2100 of the tibial prosthesis keel 2120, the punch portion2140 of the keel punch, and the 2.5 mm drill pivot cuts 2160. As shownin FIGS. 37C-D, a central axis of each pivot cut 2160 is preferablylocated adjacent a major striation 2124 of the tibial prosthesis keel2120. FIG. 37D shows that the successive 2.5 mm drill pivot cuts 2160located adjacent major striations 2124 of tibial prosthesis keel 2120result in approximately 0.021″ interference with a major striation 2164of the successive 2.5 mm drill pivot cuts 2160. Also shown in FIG. 37Dis that there is approximately 0.045″ interference created between aminor striation 2162 of the successive 2.5 mm drill pivot cuts 2160 andminor striations 2122 of tibial prosthesis keel 2120.

FIG. 38A is a perspective view of an embodiment of a tibial prosthesiskeel 2220 having a custom keel shape around a portion of an outerperimeter 2222 thereof. FIG. 38B is an embodiment of a 0.5° drafted endmill 2240. The custom keel shape shown in FIG. 38A can be prepared usingmultiple plunge cuts with end mill 2240. Leading edge cuts are madeusing end mill 2240 while following shape of outer perimeter 2222 oftibial prosthesis keel 2220. Such cuts will compress cancellous bone forreceipt of tibial prosthesis keel 2220 creating a greater compressionfit.

Prior to finishing off certain bone cuts with an accurate cut using aburr and robot, for example, debulking is generally performed to removea majority of bone as a first pass before such a finishing pass isperformed. While debulking is performed to remove a majority of bone, asufficient amount of bone must be preserved such that subsequentadjustments to all degrees of freedom of an implant that will beimplanted on the resected surface can still be done. In a finishingpass, 1-2 mm layer of remaining bone on all cut surfaces is removed.Final adjustments to implant position and shape is made during afinishing pass. This may include a scalloped surface finish for receiptof certain shaped implants.

FIGS. 39A and 39B are perspective views of the proximal tibia 2300 afterbicruciate retaining debulking and finishing is performed. As shownthere is an outer tool boundary region 2320, a cortical rim region 2340and a cancellous bone region 2360. These regions may vary in sizedepending on the diameter of the debulking cutter used. For example, a3, 4 or 5 mm diameter debulking cutter may be used to create thedebulking cutter radius all around the proximal tibia as shown in toolboundary region 2320. Preferably, a 3.2 mm burr is used to create afinishing cutter radius 2380 formed around the eminence. As shown inFIG. 39C, there is a dotted line 2330 in which a 3.2 mm burr is used formachining a keel 2352 and pegs 2354 for a tibial baseplate 2350.

For peg preparation, an interference fit between the bone and theimplant is often desired to achieve adequate fixation. With the robot,this level of interference can be customized. The robot will machineaway an opening in the bone into which the implant will be impacted, andthe diameter of the opening can be tailored to achieve a desired levelof interference. For example, a smaller peg hole diameter can beprepared to achieve greater interference between the bone and theimplant.

FIGS. 40, 41 and 42 are perspective views of the distal femur afterdebulking and finishing is performed. As shown in FIG. 40, distal femur2400 includes an outer tool boundary region 2420, a cortical rim region2440 and a cancellous bone region 2460. A portion of outer tool boundaryregion 2420 bounds a cruciate retaining region 2480. As shown in FIG.41, distal femur 2500 includes an outer tool boundary region 2520, acortical rim region 2540 and a cancellous bone region 2560. A portion ofouter tool boundary region 2520 bounds a posterior stabilization region2580. As shown in FIG. 42, distal femur 2600 includes a partial kneeresurfacing region having an outer tool boundary region 2620, a corticalrim region 2640 and a cancellous bone region 2660. A region 2680 isshown where a finishing cutter is used to minimize the resultant gapbetween implant and cartilage. FIG. 43A is a side view and FIG. 43B is aplan view of a unicondylar prosthesis 2700 on the partial kneeresurfacing region of FIG. 42.

Traditionally, an interference fit is created between the pegs on theimplant and the peg preparation in the bone for cementless femoral totalknee arthroplasty (“TKA”) procedures. Additionally, interference can becreated between the implant and the anterior and posterior boneresections. The following embodiments discuss bone preparation methodsintended to create additional press-fit between a cementless femoral TKAand the prepared bone. An interference press fit is created between theimplant and the bone by preparing the bone with a rib-like pattern onthe anterior bone cut surface. The ribs are intended to compact uponimpaction of the femoral component. Preferably, the ribs extend alongthe most anterior bone cut surface, and run distal to posterior,parallel to the intended anterior bone cut surface of the implant.

As shown in FIG. 44A, distal femur 2700 includes a tolerance profile orribs 2720 extending along an anterior bone cut surface. When an implantis introduced onto the bone, the ribs 2720 compact and achieve aninterference fit between the implant and the bone. FIG. 44B shows across-sectional view of ribs 2720 of FIG. 44A. The three-dimensionalgeometry of ribs 2720 is the result of a rotational cutting tool, suchas a burr for example, making a plurality of channeled preparations 2722into distal femur 2700. In the embodiment shown, the plurality ofchanneled preparations 2722 follow a substantially linear path. Ribs2720 have a height 2724, a width 2726 and a plurality of protrusions2728. Ribs 2720 shown on distal femur 2700 are similar to the toleranceprofile 30 shown in FIGS. 3 and 4, for example. In this embodiment, theradius of the finishing burr is preferably 2.5-3.5 mm.

As shown in FIG. 45, distal femur 2800 includes an MMC implant profile.The peak-to-peak distance between adjacent ribs 2820 can be adjusted tohave more or less interference press fit and compaction. Width 2826 ofribs 2820 is defined as the distance from bone peak 2882 to adjacentpeak in a transverse direction.

FIG. 46 shows distal femur 2900 including a LMC implant profile. Thebone will be compacted approximately 0.01″ upon implantion of the LMCimplant. This compaction is shown as the linear distance between a firstline adjacent bone peak 2982 and a second line closer to valley 2984.

In other embodiments, this concept of highly toleranced zones of bonepreparation may be used for other bone preparation and prostheticimplants throughout the body. Other areas and uses may includebicompartmental knee replacement implants, tricompartmental kneereplacement implants, total knee replacement implants, patellofemoralreplacement implants, acetabular cup implants, spinal interbody devices,and vertebral body replacements.

1. A method of preparing a bone surface to receive a prosthetic implantthereon, the prosthetic implant having an articular surface and a bonecontacting surface, the method comprising: resecting the bone surface ata first location to create a first resected region having a firstcross-section; resecting the bone surface at a second location to createa second resected region having a second cross-section different thanthe first cross-section; and contacting respective first and secondsurfaces of the bone contacting surface of the prosthetic implant withthe first and second resected regions of the bone surface, the firstsurface having a first geometry and the second surface having a secondgeometry different than the first geometry.
 2. The method of claim 1,wherein the first cross-section has peaks and valleys and the secondcross-section is less dense than the first cross-section such that thesecond cross-section has at least one of peaks further apart and valleysof different heights than the respective peaks and valleys of the firstcross-section.
 3. The method of claim 1, further comprising: forming atleast one recess in the bone surface prior to implanting the prostheticimplant on the bone surface; and inserting a retention element extendingfrom the bone contacting surface in the at least one recess in the bonesurface.
 4. The method of claim 2, including applying downward force tothe articular surface of the prosthetic implant to compact bone in thefirst resected region.
 5. The method of claim 1, further comprising:resecting the bone surface at a plurality of locations to create aplurality of resected regions each having a different cross-section. 6.The method of claim 5, wherein a first of the plurality of resectedregions is located at an anterior aspect of the bone surface.
 7. Themethod of claim 6, wherein a second of the plurality of resected regionsis located at an outer aspect of the bone surface.
 8. The method ofclaim 7, wherein a third of the plurality of resected regions is locatedat a posterior aspect of the bone surface.
 9. The method of claim 8,wherein the cross-section of the first of the plurality of resectedregions is less dense than the cross-section of the second of theplurality of resected regions and is more dense than the cross-sectionof the third of the plurality of resected regions.
 10. A method ofpreparing a bone surface to receive a prosthetic implant thereon, theprosthetic implant having an articular surface and a bone contactingsurface, the method comprising: resecting the bone surface at ananterior aspect thereof to create a first resected region having a firstcross-section; resecting the bone surface at a posterior aspect thereofto create a second resected region having a second cross-section; andcontacting respective first and second surfaces of the bone contactingsurface of the prosthetic implant with the first and second resectedregions of the bone surface, the first surface having a first geometryand the second surface having a second geometry different than the firstgeometry.
 11. The method of claim 10, wherein the first cross-sectionhas peaks and valleys and the second cross-section is less dense thanthe first cross-section such that the second cross-section has at leastone of peaks further apart and valleys of different heights than therespective peaks and valleys of the first cross-section.
 12. The methodof claim 10, further comprising: forming at least one recess in the bonesurface prior to implanting the prosthetic implant on the bone surface;and inserting a retention element extending from the bone contactingsurface in the at least one recess in the bone surface.
 13. The methodof claim 11, including applying downward force to the articular surfaceof the prosthetic implant to compact bone in the first resected region.14. The method of claim 10, further comprising: resecting the bonesurface at a plurality of locations to create a plurality of resectedregions each having a different cross-section.
 15. A method of preparinga bone surface to receive a prosthetic implant thereon, the prostheticimplant having an articular surface and a bone contacting surface, themethod comprising: resecting the bone surface at a peripheral regionthereof to create a first resected region having a first cross-section;resecting the bone surface at an anterior region thereof to create asecond resected region having a second cross-section; and contactingrespective first and second surfaces of the bone contacting surface ofthe prosthetic implant with the first and second resected regions of thebone surface, the first surface having a first geometry and the secondsurface having a second geometry different than the first geometry. 16.The method of claim 15, wherein the first cross-section has peaks andvalleys and the second cross-section is less dense than the firstcross-section such that the second cross-section has at least one ofpeaks further apart and valleys of different heights than the respectivepeaks and valleys of the first cross-section.
 17. The method of claim15, further comprising: forming at least one recess in the bone surfaceprior to implanting the prosthetic implant on the bone surface; andinserting a retention element extending from the bone contacting surfacein the at least one recess in the bone surface.
 18. The method of claim16, including applying downward force to the articular surface of theprosthetic implant to compact bone in the first resected region.
 19. Themethod of claim 15, further comprising: resecting the bone surface at aplurality of locations to create a plurality of resected regions eachhaving a different cross-section.